Encoding uplink acknowledgments to downlink transmissions

ABSTRACT

A portable device, such as a mobile terminal or user equipment, for encoding uplink acknowledgments to downlink transmissions. The portable device includes a receiver configured to receive a plurality of data blocks, such that each of the data blocks include an associated cyclic redundancy check (CRC), and a processor configured to determine received status for each of the data blocks by checking the CRC of each of the data blocks. The portable device further includes a transmitter for transmitting a response sequence which indicates the received status of all of the data blocks.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application Nos.10-2006-0054564, filed on Jun. 16, 2006, 10-2006-0054563, filed on Jun.16, 2006, and 10-2006-0074636, filed Aug. 8, 2006, and pursuant to 35U.S.C. §119(e), this application further claims benefit of priority fromprovisional patent application 60/805,059, filed Jun. 16, 2006. Thecontents of such applications are hereby incorporated by referenceherein in their entirety

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communications, and inparticular, to encoding uplink acknowledgments to downlinktransmissions.

2. Discussion of the Related Art

One multiple carrier communication scheme transmits data through anumber of orthogonal subcarriers. Examples of such systems, whichtypically require a high data rate, include wireless location areanetworks (LANs) and mobile Internet technologies. Typical multiplecarrier communication schemes include orthogonal frequency divisionmultiplexing (OFDM), discrete Fourier transform-spreading-orthogonalfrequency division multiplexing (DFT-S-OFDM or DFT-Spreading-OFDM) (alsoreferred to as SC-FDMA), and orthogonal frequency division multiplexingaccess (OFDMA). Although OFDM and OFDMA can achieve a high transfer rateby keeping subcarriers orthogonal, such techniques often have a highpeak-to-average power ratio (PAPR). DFT-S-OFDMA is a technique which maybe implemented to overcome the PAPR problem, for example. DFT-S-OFDMAfunctions by first spreading signals with a DFT matrix in the frequencydomain before generating OFDM signals. The signals which were spread maythen be modulated and transmitting in known fashion using conventionalOFDM techniques. This technique will now be described.

FIG. 1 is a flowchart depicting the generation of a transmission signalaccording to a conventional DFT-S-OFDMA system. According to blocks 110and 120, a typical DFT-S-OFDM wireless communication system spreadssignals using a DFT matrix before generating the OFDM signals. Consideran equation in which “s” is an input data symbol, “x” is data spread inthe frequency domain, and “N_(b)” is the number of subcarriers for aparticular user. In such a scenario, the spread data “x” may be obtainedusing the following:

x=F _(N) _(b) _(×N) _(b) S,

where F_(N) _(b) _(×N) _(b) is a N_(b)×N_(b) DFT matrix used to spreadthe input data symbol.

According to blocks 130, 140, and 150, the spread vector “x” is shownmapped to a subcarrier according to a subcarrier mapping technique, andis then transformed into the time domain through an inverse discreteFourier transform (IDFT) module to obtain a signal for transmission to areceiving entity. The transmission signal “y” may be obtained using thefollowing:

y=F _(N×N) ⁻¹ x,

where F_(N×N) is an N×N DFT matrix used to transform a frequency domainsignal into a time domain signal. The signal “y” generated in thismanner is transmitted with an inserted cyclic prefix (block 160).

Data, pilots, and control information are then transmitted in the uplinkof multiple carrier systems, including, for example, the DFT-S-OFDMsystem. Control information can be divided into data-associated controlinformation, which is associated with data demodulation, andnon-data-associated control information, which is not associated withdata demodulation.

Data-associated control information includes control informationrequired to reconstruct data transmitted by user equipment (UE). Forexample, data-associated control information may include informationassociated with the transmit format or information associated withhybrid automatic repeat-request (HARQ). The amount of thedata-associated control information can be adjusted according to anuplink data scheduling scheme.

On the other hand, non-data-associated control information is controlinformation required for downlink transmission. For example, thenon-data-associated control information may include acknowledgment (ACK)or negative acknowledgment (NACK) information for HARQ operation, and achannel quality indicator (CQI) for link adaptation of the downlink.

In an uplink multi-carrier or single-carrier FDMA system, controlinformation is divided into a data-associated control information fordemodulating user data and non-data-associated control information fordownlink transmission. A basic principle of OFDM includes dividing adata stream having a high data rate into a plurality of data streams,each of which has a slow data rate, and then transmitting the datastreams simultaneously using a plurality of carriers. Each the carriersis referred to as a subcarrier. Since orthogonality exists between thecarriers of OFDM, if frequency components of the carriers are overlappedwith each other, a transmitting terminal can still detect the frequencycomponents.

The data stream having the high data rate is converted to a plurality ofdata streams having slow data rates via a serial to parallel converter.Each of the parallel-converted data streams is multiplied by acorresponding subcarrier, added together, and then transmitted to thereceiving terminal.

The parallel data streams generated by the serial to parallel convertercan be transmitted as a plurality of subcarriers by IDFT. IDFT can beefficiently implemented using an inverse fast Fourier transform (IFFT).

As symbol duration of the subcarrier having the slow data rateincreases, relative signal dispersion, which occurs by multi-path delayspreading, decreases on the time domain. Inter-symbol interference maybe reduced by inserting a guard interval longer than the channel delayspreading between OFDM symbols. If a portion of an OFDM signal is copiedto the guard interval and arranged at a start portion of the symbol, theOFDM symbol is cyclically extended to be protected.

The amount of frequency resources used for data transmission may bereduced if the UE allocates a sufficient number of subcarriers tonon-data-associated control information when transmitting the controlinformation in the uplink. This technique consequently results in alarge number of subcarriers which are unable to be allocated, thusaffecting the ability to achieve diversity gain in the frequency domain.

A typical UE separately transmits ACK/NACK and CQI signals amongnon-data-associated control information in the uplink. For example, theUE transmits the ACK/NACK signal, the CQI signal, or both of thesesignals at a particular time period. However, conventional multiplecarrier systems do not typically distinguish between such signals whenprocessing the non-data-associated control information. This preventsefficient utilization of frequency resources.

If ACK/NACK and CQI signals are transmitted using a single discreteFourier transform (DFT) in the uplink of the DFT-S-OFDM communicationsystem, a number of users will typically share the same resource unit.For instance, if one user transmits an ACK/NACK signal and another usertransmits a CQI signal with the same resource unit, it may not bepossible for a base station to demodulate the ACK/NACK and CQI signalsof the two users.

SUMMARY OF THE INVENTION

Features and advantages of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

In accordance with an embodiment, a method for encoding uplinkacknowledgments to downlink transmissions includes receiving a pluralityof data blocks, such that each of the data blocks include an associatedcyclic redundancy check (CRC). The method further includes determiningreceived status for each of the data blocks by checking the CRC of eachof the data blocks, and generating a response sequence which indicatesthe received status of all of the data blocks.

According to one feature, the data blocks include a primary transportblock and a secondary transport block.

According to another feature, the response sequence is a discreteresponse sequence.

According to yet another feature, the method further includes generatingthe response sequence as a single response sequence which indicates thereceived status of all of the data blocks.

According to still yet another feature, the receiving of the data blocksis from a Node B.

According to one aspect, the status is either an acknowledgment (ACK)which identifies a data block which has been received without error, ora negative acknowledgment (NACK) which identifies a data block which hasbeen received with an error.

According to another aspect, the method further includes modulating theresponse sequence using QPSK modulation.

According to yet another aspect, the method further includestransmitting the response sequence to a Node B.

According to still yet another aspect, the downlink transmissionsinclude multiple input multiple output (MIMO) transmissions.

According to one feature, the method further includes receiving the datablocks in parallel.

According to another feature, the downlink transmissions comprise timedivision duplex (TDD) transmissions.

According to yet another feature, the method further includes eithersequentially receiving the data blocks or receiving the data blocks inparallel.

In accordance with an alternative embodiment, a method for receivingencoded uplink acknowledgments to downlink transmissions includestransmitting in parallel a plurality of data blocks, such that each ofthe data blocks include an associated cyclic redundancy check (CRC). Themethod further includes receiving a single response sequence whichindicates received status of all of the data blocks.

In accordance with another alternative embodiment, a portable device forencoding uplink acknowledgments to downlink transmissions includes areceiver configured to receive a plurality of data blocks, such thateach of the data blocks include an associated cyclic redundancy check(CRC), and a processor configured to determine received status for eachof the data blocks by checking the CRC of each of the data blocks. Theportable device further includes a transmitter for transmitting aresponse sequence which indicates the received status of all of the datablocks.

In accordance with yet another embodiment, a transmitting entityoperable in a wireless communication system and configured to receiveencoded uplink acknowledgments to downlink transmissions includes atransmitter for transmitting in parallel a plurality of data blocks,such that each of the data blocks include an associated cyclicredundancy check (CRC), and a receiver for receiving a single responsesequence which indicates received status of all of the data blocks.

In accordance with still yet another embodiment, a method for encodinguplink acknowledgments to downlink transmissions includes receiving aplurality of data blocks, such that each of the data blocks include anassociated cyclic redundancy check (CRC), determining received statusfor each of the data blocks by checking the CRC of each of the datablocks, and generating a response bit according to the status. Themethod further includes mapping the response bit to a fixed lengthsequence to generate a mapped sequence, transmitting the mapped sequencein an uplink transmission, and repeating the mapping and transmittingfor a predetermined time period.

These and other embodiments will also become readily apparent to thoseskilled in the art from the following detailed description of theembodiments having reference to the attached figures, the invention notbeing limited to any particular embodiment disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will become more apparent upon consideration of the followingdescription of preferred embodiments, taken in conjunction with theaccompanying drawing figures, wherein:

FIG. 1 is a flowchart depicting the generation of a transmission signalaccording to a conventional DFT-S-OFDMA system;

FIG. 2A shows a UE transmitting in the uplink to collectively spread thecontrol information vectors to obtain a spread vector;

FIG. 2B shows another arrangement for uplink transmissions in aDFT-S-OFDM wireless communication system according to an alternativeembodiment of the present invention;

FIG. 2C shows yet another arrangement for uplink transmissions in aDFT-S-OFDM wireless communication system according to an alternativeembodiment of the present invention;

FIG. 3A depicts an uplink subframe format using time divisionmultiplexing (TDM) in a DFT-S-OFDM wireless communication system;

FIG. 3B depicts an uplink subframe format using frequency divisionmultiplexing (FDM) in a DFT-S-OFDM wireless communication system;

FIGS. 4A and 4B are block diagrams depicting techniques for reducing theBER in a transmitting UE operating within a DFT-S-OFDM wirelesscommunication system according to an embodiment of the presentinvention;

FIG. 5 is a block diagram depicting a method for selecting a subcarrierto be allocated according to an embodiment of the present invention;

FIG. 6 shows an uplink subframe format;

FIGS. 7 and 8 depict uplink multiplexing schemes;

FIGS. 9A-9C depict embodiments which relates to allocating a frequencyresource for ACK/NACK signal transmission in the uplink of aSC-FDMA/OFDMA system;

FIGS. 10A and 10B are block diagrams depicting SCW and MCW transmittingterminals configured for use in a MIMO wireless mobile communicationsystem;

FIG. 11 is a block diagram of an ACK/NACK transmitting apparatusaccording to an embodiment of the present invention;

FIG. 12 is a block diagram of an ACK/NACK transmitting apparatusaccording to another embodiment of the present invention;

FIG. 13A depicts localized allocation of a number of subcarriers;

FIG. 13B depicts distributed allocation of a number of subcarriers;

FIG. 14 is a block diagram depicting a method for uplink transmissionusing OFDM;

FIG. 15 is a flowchart depicting the generation of a transmission signalaccording to DFT-S-OFDMA;

FIG. 16 provides an example of closely arranged subcarriers;

FIG. 17 provides an example of a subcarrier arrangement using enhancedlocalized allocation;

FIG. 18 shows a distribution of subcarriers used for ACK/NACK signaltransmission;

FIGS. 19A and 19B depict a subcarrier arrangement using enhanceddistributed allocation, in which a pair of subcarriers is configured asa group; and

FIGS. 20A and 20B depict further subcarrier arrangements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawing figures which form a part hereof, and which show byway of illustration specific embodiments of the invention. It is to beunderstood by those of ordinary skill in this technological field thatother embodiments may be utilized, and structural, electrical, as wellas procedural changes may be made without departing from the scope ofthe present invention. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or similarparts.

Various embodiments will be described in conjunction with a UE. However,such teachings apply also to other types of wireless terminals such asmobile terminals, mobile stations, and the like.

Spreading of Control Information Vectors in Uplink

FIGS. 2A-2C are block diagrams which illustrate various elements of anuplink transmitting entity operable within a DFT-S-OFDM wirelesscommunication system in accordance with an embodiment of the presentinvention. Consider first a UE configured as the transmitting entity insuch a communication system. The UE may receive and distinguish controlinformation such as ACK/NACK, a channel quality indicator (CQI), andother types of non-data-associated control information. Such controlinformation is not associated with data demodulation. Generally, anACK/NACK is a vector that includes one or more bits which are based uponthe number of cyclic redundancy codes (CRCs) inserted into the downlinksignal. The CQI is a vector that generally includes a plurality of bitsto report a channel quality state to an associated base station or NodeB, for example. The CQI facilitates downlink scheduling at the basestation. By way of non-limiting example, embodiments will be describedin which the size of the ACK/NACK vector is “1” and the size of the CQIvector is “m.”

FIG. 2A shows a UE transmitting in the uplink to collectively spread thecontrol information vectors (sized 1+m through DFT) to obtain a spreadvector (X′_(ACK+CQI)) with a size of n bits (n=1+m), withoutdistinguishing between the ACK/NACK vector of size 1 and the CQI vectorof size m. Another operation performs an inverse fast Fourier transform(IFFT) on vector (X″_(ACK+CQI)) obtained through subcarrier mapping toacquire and transmit time information (y_(ACK+CQI)).

In this scenario, if one UE transmits an ACK/NACK and another UEtransmits CQI using the same resource block, it is difficult for areceiving base station to select an IDFT for despreading a vectorX′_(ACK+CQI) that is obtained by removing each subcarrier from a vectorX″_(ACK+CQI). The vector X″_(ACK+CQI.) may be obtained by the basestation through a fast Fourier transform (FFT) which corresponds to theIFFT performed at the transmitting end. Signals transmitted by the UEsare typically indistinguishably spread in the vector X″_(ACK+CQI) andthe vector X′_(ACK+CQI). This is because it may be necessary todistinguish between IDFTs used to analyze received signals from two ormore UEs, if the UEs use the same resource block.

FIG. 2B shows another arrangement for uplink transmissions in aDFT-S-OFDM wireless communication system according to an alternativeembodiment of the present invention. A UE configured to transmitaccording to this figure distinguishes and receives various types ofcontrol information (described above). In this example, the UE spreadsthe ACK/NACK and CQI control information using different DFTs beforemapping these parameters to corresponding subcarriers. Since theACK/NACK vector (X_(ACK)) of size 1 and the CQI vector (X_(CQI)) of sizem are spread using different DFTs, their spread vectors (X′_(ACK)) and(X′_(CQI)) of size 1 and m, respectively, also include ACK/NACKinformation and CQI information.

The spread vectors (X′_(ACK)) and (X′_(CQI)) are shown mapped tocorresponding subcarriers, which are subjected to the IFFT andsubsequently transmitted to the base station. According to thisembodiment, if one UE transmits an ACK/NACK and another UE transmits CQIusing the same resource block, the base station can easily select IDFTsfor despreading vectors X′_(ACK) and X′_(CQI) that are each obtained byrespectively removing subcarriers from vectors X″_(ACK) and X″_(CQI).The vectors X″_(ACK) and X″_(CQI) may be obtained by the base stationthrough a FFT corresponding to the IFFT that was performed at thetransmitting end, which in the illustrated case is the UE.

FIG. 2B is an example which distinguishes between control informationsuch as ACK/NACK and CQI. However other types of information may besimilarly distinguished using the illustrated techniques. For example,the techniques of this figure may also be applied to situations in whichtwo or more control signals (or information) are received and spreadusing different DFTs before being mapped to a frequency resource fortransmission through the uplink. This allows a receiving entity, whichreceives the uplink signal, to distinguish between the transmitted twoor more types of control information through control information that isdemapped from the frequency resource.

The embodiment of FIG. 2B separately spreads control information usingseparate DFTs, but alternatives are possible and envisioned by thepresent disclosure. For example, the separate DFT processes mayalternatively include any process, provided that such processes allowthe entity receiving the uplink signal to distinguish between thedifferent types of control information.

FIG. 2C shows another arrangement for uplink transmissions in aDFT-S-OFDM wireless communication system according to an alternativeembodiment of the present invention. In this embodiment, thetransmitting UE, for example, directly maps ACK/NACK control informationto a subcarrier. This is accomplished without performing DFT, andresults in obtaining the vector X″_(ACK). FIG. 2C further showstransforming CQI control information using a DFT, and then mapping theresulting spread vector X′_(CQI) to a subcarrier to obtain a vectorX″_(CQI).

Generally, the size of the vector corresponding to the ACK/NACKinformation is smaller than the size of the vector corresponding to theCQI information. Thus the effects achieved by spreading the vectorcorresponding to the ACK/NACK information are relatively small. Thisembodiment is simplified to the extent that the DFT processing of theACK/NACK signal is omitted. However, this embodiment achieves effectssimilar to those of the case of FIG. 2B since the base station cancorrectly distinguish between information items that have been subjectedto a FFT. If desired, the embodiment of FIG. 2C may alternativelyinclude any separate process, other than the separate DFT spreading,provided that such a process allows the receiving entity to distinguishbetween the different types of control information.

The embodiment of FIG. 2C may further include a structure for improvingpeak-to-average power ratio (PAPR) performance. For example, if theACK/NACK signal is directly mapped to a subcarrier without DFT, and itis then subjected to IFFT for transmission, the compensation effectsbetween DFT and IFFT may degrade the PAPR performance (relative toperformance which may be achieved by the configuration of FIG. 2B). Assuch, a UE configured in accordance with FIG. 2C may select a specificsubcarrier for improving the PAPR performance, and then map the ACK/NACKsignal to the selected subcarrier.

FIG. 3A depicts an uplink subframe format using time divisionmultiplexing (TDM) in a DFT-S-OFDM wireless communication system. FIG.3B depicts an uplink subframe format using frequency divisionmultiplexing (FDM) in a DFT-S-OFDM wireless communication system.

Generally, ACK/NACK control information in a DFT-S-OFDM wirelesscommunication system is represented by either one bit, or a relativelysmall number of bits. Consequently, the bit error rate (BER) may besomewhat degraded because of various factors in a wireless channel.Typical multiplexing methods in the DFT-S-OFDM wireless communicationsystem include TDM (FIG. 3A) and FDM (FIG. 3B). Accordingly, atransmitting UE in accordance with an embodiment will typicallyrepeatedly transmit ACK/NACK information to improve the BER.

Consider the case in which TDM is used by several UEs. In such ascenario ACK/NACK information may be repeatedly transmitted in a longblock (LB) allocated in a subframe (e.g., LB #3 of FIG. 3A) over aspecific frequency. Such an arrangement will typically improve the BERcharacteristics.

Repeated transmissions over a specific frequency may be accomplished bysequentially transmitting ACK/NACK information over a frequency band, orby mapping ACK/NACK information to a specific sequence. DFT mayoptionally be performed on this ACK/NACK information. If desired,ACK/NACK information may also be repeatedly transmitted using blockcoding.

Consider now situations in which FDM is used to multiplex informationtransmitted from multiple UEs. In such scenarios, ACK/NACK informationmay be repeatedly transmitted in multiple LBs allocated in a subframe(e.g., LB #1-LB #6 of FIG. 3B). Such an arrangement will also typicallyimprove the BER characteristics. In some cases, multiple ACK/NACKsignals may be transmitted in response to downlink information usingmultiple antennas. In an embodiment, the number of ACK/NACK signals isequal to the number of CRCs inserted in the downlink data (as describedabove).

A UE may responsively transmit (uplink) a number of ACK/NACK signalscorresponding to the number of received CRCs for situations in which aCRC is inserted in each portion of information transmitted through eachof the antennas in the downlink. If the UE transmits a plurality ofACK/NACK signals in this manner, the UE may also repeatedly transmit theACK/NACK signals a specific number of times. Such operations may be usedto improve BER characteristics of the transmitted ACK/NACK signals.

For example, consider that the number of ACK/NACK signals is M. The MACK/NACK signals may be denoted by ACK/NACK₁, ACK/NACK₂, . . . ,ACK/NACK_(M), and the specific number of times is K. In this case, theACK/NACK signals may be repeatedly transmitted according to thefollowing:

{(ACK/NACK₁₋₁, ACK/NACK₁₋₂, . . . ACK/NACK_(1-K)), {(ACK/NACK₂₋₁,ACK/NACK₂₋₂, . . . ACK/NACK_(2-K)), . . . , (ACK/NACK_(M-1),ACK/NACK_(M-2), . . . ACK/NACK_(M-K)}.)

According to an alternative technique, ACK/NACK signals may berepeatedly transmitted according to the following:

{(ACK/NACK₁₋₁, ACK/NACK₂₋₁, . . . ACK/NACK_(M-1)), {(ACK/NACK₁₋₂,ACK/NACK₂₋₂, . . . ACK/NACK_(M-2)), . . . , (ACK/NACK_(1-K),ACK/NACK_(2-K), . . . ACK/NACK_(M-K))}.

FIGS. 4A and 4B are block diagrams depicting techniques for reducing theBER in a transmitting UE operating within a DFT-S-OFDM wirelesscommunication system according to an embodiment of the presentinvention. Consider first the situation in which the transmitting endtransmits multiple ACK/NACK signals using multiple antennas. In such acase, the transmitting end may transmit the ACK/NACK signals byperforming block coding on these signals using, for example, thetechniques shown in FIGS. 4A and 4B.

Referring now to FIG. 4A, a technique is shown in which prior totransmitting, the ACK/NACK and CQI signals are first spread usingseparate DFTs. An alternative technique is shown in FIG. 4B. In thisfigure, the ACK/NACK signals are directly mapped to a subcarrier withoutspreading these signals through a DFT. However, the embodiment of FIG.4B includes mapping the CQI signal to a subcarrier after spreading thissignal using a DFT.

Multiple ACK/NACK signals for improving the PAPR and BER characteristicsof ACK/NACK signals need not be directly transmitted, and instead mayalternatively be mapped to a specific sequence to be transmitted.According to one technique, a specific sequence for mapping may bedetermined A sequence may be selected and a plurality of ACK/NACKsignals mapped to the sequence. If desired, the sequence may be selectedas the specific sequence for mapping according to its PAPR and BERcharacteristics. Another option includes transmitting ACK/NACK signalsafter modulating these signals using a conventional modulation techniquesuch as BPSK or QPSK.

FIG. 5 is a block diagram depicting a method for selecting a subcarrierto be allocated according to an embodiment of the present invention.This technique selects the subcarrier based upon transmission status ofthe ACK/NACK and CQI information and when such information istransmitted.

Allocating a sufficiently large number of subcarriers tonon-data-associated control information in the uplink may reduce thenumber of subcarriers necessary to transmit UE data. ACK/NACK and CQIinformation may be separately transmitted, as described above. However,frequency resources may be efficiently allocated if subcarrierallocation is also performed when both the ACK/NACK and CQI informationis transmitted. This is particularly the case where, withoutdiscriminating between the cases where only the ACK/NACK information istransmitted, only the CQI information is transmitted or where theACK/NACK and CQI information are simultaneously transmitted.

Accordingly, a transmitting UE according to an embodiment of the presentinvention may distinguish and receive ACK/NACK and CQI information,among non-data-associated control information, to identify whether eachof the ACK/NACK and CQI information is transmitted. Based on thisidentification, the UE may allocate a subcarrier suitable for each casein which only the ACK/NACK information is transmitted, or where only theCQI information is transmitted, or where both the ACK/NACK and CQIinformation are simultaneously transmitted. This embodimentdistinguishes between ACK/NACK and CQI information amongnon-data-associated control information to identify whether each of theACK/NACK and CQI information is transmitted. This embodiment efficientlymanages frequency resources, and permits allocation of increased amountsof frequency resources for transmission, thereby achieving frequencydiversity.

Advantages of various embodiments include the UE distinguishing ACK/NACKand CQI information, among non-data-associated control information whichis not associated with data demodulation, and separately processing suchinformation before it is mapped to frequency resources. This allows abase station to easily process received control information, even whenthe base station separately receives ACK/NACK and CQI information frommultiple UEs through the same resource block. Moreover, improvement ofthe BER characteristics of the ACK/NACK information may be accomplishedby repeatedly transmitting the ACK/NACK information in the uplink over aspecific time period when FDM is employed, or over a specific frequencywhen TDM is employed.

When multiple ACK/NACK signals are transmitted, improvement of the PAPRand/or BER characteristics may also be accomplished by performingprocesses on the transmitted ACK/NACK signals. Examples of such signalsinclude block coding, mapping to a specific sequence, and modulationthrough BPSK or QPSK.

Allocating Frequency Resource

Additional alternative embodiments relate to allocating frequencyresources for ACK/NACK transmissions in uplink multi-carrier orsingle-carrier (SC) FDMA systems. FIG. 6 shows an uplink subframeformat. In this figure, a long block (LB) is used for data and controlinformation transmissions, and a short block (SB) is used for pilot anddata transmissions.

Uplink transmission by the UE may be classified into the followingcases:

UE data, pilot, data-associated control;

UE data, pilot, data-associated control, non-data-associated control;and

Pilot, non-data-associated control.

These cases may be multiplexed using, for example, the variousmultiplexing techniques shown in FIG. 7 and FIG. 8. The subframe formatof FIG. 6 includes multiplexing data-associated control information andnon-data-associated control information with UE data, and simultaneouslymultiplexing non-data-associated control information of several UEs.

In FIG. 7, although data-associated control information and UE data aremultiplexed, a predetermined time-frequency domain is decided for thetransmission of non-data-associated control information of several UEs.If UE data exists, non-data-associated control information is showntransmitted on the band for the transmission of UE data, instead of theband decided for the non-data-associated control information on which UEdata is transmitted. A benefit of this technique is to maintain theSC-FDMA characteristics.

As shown in FIGS. 7 and 8, band allocations of UE data andnon-data-associated control are performed in the same manner. Inparticular, when the UE data corresponds to localized allocation, thelocalized allocation is applied to the non-data-associated control aswell. However, ACK/NACK information among the non-data-associatedcontrol information has a size of one bit and is therefore unable to bechannel coded. Consequently, iteration of the ACK/NACK information maybe performed to obtain a specific error rate.

FIGS. 9A-9C depict embodiments which relate to allocating a frequencyresource for ACK/NACK signal transmission in the uplink of aSC-FDMA/OFDMA system, and variations thereof In general, there are twotechniques for allocating a frequency resource in the uplink. The firsttechnique being a distributed method of arranging transmission data withthe same interval on entire frequency bands (FIG. 9A). The secondtechnique being a localized method of arranging transmission data on aspecific frequency band (FIGS. 9B, 9C).

Although the ACK/NACK signal is typically one bit in size, iteration ofthis signal may be performed to obtain a specific error rate. Forexample, consider that the ACK/NACK signal obtained from iteration istransmitted via N resource units (RU). In transmitting the ACK/NACKsignal iterated using a localized method though N RUs, if the ACK/NACKis smaller than a frequency resource occupied by the N RUs, the twoadditional methods may also be implemented. One technique is to allocatean iterated ACK/NACK signal to continuous frequency resources, while theother technique is to arrange the ACK/NACK signal on N RUs using, forexample, an even interval. Accordingly, techniques for allocatingfrequency resources for ACK/NACK transmission may be summarized asfollows:

Distributed;

Localized;

Pure localized; and

Distributed within allocated frequency resources.

Multiple Codeword ACK/NACK

Yet another embodiment relates to HARQ in a mobile communication system,and more particularly, to an apparatus for transmitting ACK/NACK signalin a multiple codeword (MCW) type MIMO wireless system. As will bedescribed, this embodiment is suitable for a wide scope of applicationsincluding, for example, transmitting the ACK/NACK signal using multipleMCW type transmitting and receiving antennas.

In general, multiple transmitting and receiving antennas may be used toraise the data rate in a mobile communication system. Data transmissionusing multiple antennas may be accomplished using two primarytechniques. First, data may be transmitted in a transmit diversityformat. In this case, although a data rate is not raised, a signal tonoise ratio (SNR) of a received signal is raised to enable stableoperation. This is because the same data is transmitted via severalantennas. The second technique includes transmitting data in a spatialmultiplexing format. In this case, simultaneously transmitting severalindependent data streams raises the data rate. The transmit diversitytransmission is efficient in an area having a low SNR, whereas thespatial multiplexing transmission is efficient in an area having a highSNR.

FIGS. 10A and 10B are block diagrams depicting SCW and MCW transmittingterminals configured for use in a MIMO wireless mobile communicationsystem. It is understood that in some situations, a plurality of datastreams can be simultaneously transmitted. For instance, coding may beperformed by one channel encoder, and then the data is divided into aplurality of data streams. This technique is often referred to astransmitting using a single codeword (SCW).

FIG. 11 is a block diagram of an ACK/NACK transmitting apparatusaccording to an embodiment of the present invention. This exampleprovides a technique for transmitting multiple streams which includesindividually coding a plurality of data streams via a channel encoder,and then transmitting the encoded data streams via a plurality oftransmitting and receiving antennas. This technique is often referred toas transmitting using a multiple codeword (MCW).

SCW techniques include coding one block which is then divided. Since oneCRC for error checking is attached to each block, a receiver wouldtypically transmit only one ACK/NACK signal. On the other hand, usingMCW, several blocks are coded and then turned into a data stream. If CRCis attached per block, the ACK/NACK signal should be transmitted foreach data stream.

In general, the MCW is able to obtain a data rate higher than that ofthe SCW. Consequently, the MCW is commonly used despite the increase ofACK/NACK information to be transmitted. However, in situations in whichthe MCW transmits an ACK/NACK signal for each data stream, a receivershould secure radio resources for a plurality of ACK/NACK transmissions.This increase of control information decreases radio resources for thedata transmission, resulting in degraded system efficiency.

Various aspects and embodiments of the present invention will now bedescribed. In general, these examples include an apparatus fortransmitting ACK/NACK signals in MCW type MIMO wireless system. Forexample, an apparatus for transmitting ACK/NACK signals in a MCW typeMIMO wireless system by which a number of ACK/NACK signals to betransmitted can be reduced by maintaining a high data rate MCW.

One aspect includes transmitting an ACK/NACK in a wireless communicationsystem using a plurality of MCW type transmitting and receivingantennas. Various operations include generating a plurality of ACK/NACKscorresponding to a number of error detection codes inserted in aplurality of data streams received via a plurality of antennas, andgenerating an ACK/NACK by combining a plurality of the ACK/NACKs, andtransmitting the generated ACK/NACK via the antenna.

Another aspect includes generating a plurality of ACK/NACKscorresponding to a number of error detection codes inserted in aplurality of data streams received via a plurality of antennas, andgrouping a plurality of the ACK/NACKs. The method further includesgenerating one ACK/NACK per group by combining a plurality of thegrouped ACK/NACKs into a plurality of such groups, and transmitting thegenerated ACK/NACK groups via the antenna.

One aspect includes, in the grouping operation, grouping a plurality ofthe ACK/NACKs according to types of corresponding data streams.

Another aspect utilizes the error detection code as a CRC code.

Yet another aspect includes transmitting the received data streams forone timeslot via a plurality of the transmitting antennas.

Still yet another aspect includes combining a plurality of the ACK/NACKsby an AND operation.

In an embodiment, an apparatus for transmitting an ACK/NACK in awireless communication system using a plurality of MCW type transmittingand receiving antennas includes an error checking unit generating aplurality of ACK/NACKs corresponding to a number of error detectioncodes inserted into a plurality of data streams received via a pluralityof antennas. The apparatus further includes a signal combining unitgenerating one ACK/NACK by combining a plurality of the ACK/NACKs, and asignal transmitting unit transmitting the generated ACK/NACK via theantenna.

In another aspect, an apparatus includes a control unit grouping aplurality of the ACK/NACKs, a signal combining unit generating oneACK/NACK per group by combining a plurality of the grouped ACK/NACKsinto a plurality of groups, and a signal transmitting unit transmittingthe generated ACK/NACK groups via the antenna.

According to an aspect, the control unit groups a plurality of theACK/NACKs according to the types of corresponding data streams.

One aspect utilizes the error detection code as an CRC code, and thereceived data streams are transmitted for one timeslot via a pluralityof the transmitting antennas, and the signal combining unit combines aplurality of the ACK/NACKs by an AND operation.

Referring again to FIG. 11, a receiving terminal includes a plurality ofantennas. When independent data is transmitted via a plurality ofantennas to achieve a high data rate, the number of antennas of areceiving terminal should be equal to or greater than that of theantennas of the transmitting terminal FIG. 11 shows n antennas toindicate that n information streams are received.

Information (e.g., n information in FIG. 11) received via a plurality ofantennas are decoded in correspondence to the channel coding techniqueperformed by the transmitting terminal. A CRC checking unit thenperforms an error check using CRC which is included in each of thedecoded information streams. As a result of performing this CRCchecking, if an error exists, the CRC checking unit generates a NACK. Ifthere is no error, the CRC checking unit generates an ACK. Accordingly,when n different information streams are received in parallel, nACK/NACKs will be transmitted. In this case, the n received data streamsmay be assumed as data streams transmitted for one timeslot via ntransmitting antennas. If desired, the information streams within acertain timeslot may be simultaneously processed.

FIG. 11 shows n ACK/NACKs inputted to a combiner to be combined into oneACK/NACK signal. For example, n ACK/NACKs may be combined into oneACK/NACK. An AND operation is carried out to combine these signals intoone ACK/NACK. In particular, consider n ACK/NACKs such as ACK/NACK1,ACK/NACK2, . . . , ACK/NACKn. The combined ACK/NACK can be expressedaccording to the following:

ACK/NACK(Combined)=ACK/NACK1∩ACK/NACK2∩ . . . ∩ACK/NACKn,

where if data is successfully received, each of ACK/NACK1 to ACK/NACKncan have a value of 1. Otherwise, each of these ACK/NACKs can have avalue of 0.

If the combined ACK/NACK indicates 1, this could refer to the entire ndata as being successfully received. If the combined ACK/NACK indicates0, this could refer to at least one of the n data as not beingsuccessfully received. Consequently, a frequency resource for controlinformation transmission can be efficiently allocated.

FIG. 12 is a block diagram of an ACK/NACK transmitting apparatusaccording to another embodiment of the present invention. In thisembodiment, a control unit is added to the configuration shown in FIG.11, as well as a plurality of combiners.

In FIG. 12, n ACK/NACKs respectively generated by CRC checking units areinputted to a control unit. The control unit then groups the inputtedACK/NACKs into a plurality of groups. These groups can be classifiedaccording to a type of received data stream. For instance, if aprescribed portion of data is important in checking a successful datareception and needs to be separately processed, it can be separatelygrouped. Alternatively, these ACK/NACKs can be divided into a prescribednumber of groups to appropriately select the size of control informationto be transmitted regardless of the type of the received data.

As mentioned above, the grouped ACK/NACK signals are combined by aplurality of combiners to generate one ACK/NACK signal per group. Ingeneral, ACK/NACKs corresponding to a specific group may include asingle ACK/NACK. In this aspect, a corresponding ACK/NACK is processedin the same manner as other ACK/NACKs having undergone the combiningoperation without passing through a separate operation for the ACK/NACKsignal combining.

Consider further that the number of groups selected by the aboveprinciple may be equal to or smaller than m, and thus m ACK/NACKs may beobtained. The m ACK/NACKs are inputted to a transmitting unit and thentransmitted via an antenna.

The embodiments of FIGS. 11 and 12 have been described with regard tothe error detection code implemented using CRC code. Alternatively, arandom error detection code that is a signal requested by a receivingterminal may be used to be informed whether a data transmission issuccessful.

Various embodiments enable a receiving terminal to transmit ACK/NACK atthe SCW level despite using MCW having a data rate that is higher thanthat of the SCW. Alternatively, if transmission of the n data streamsfalls below a certain critical count, an ACK/NACK indicating a presenceor non-presence of a transmission success for each of the n data streamscan be transmitted without being combined instead of repeatingtransmissions of the entire n data streams. Alternatively, consider thesituation in which transmission of specific data fails a certain numberof times on the assumption that a plurality of received data streams canbe individually discriminated. ACK/NACK information for indicating apresence or non-presence of transmission success of the specific datastream is independently transmitted without combining and the remainderof ACK/NACK signals are combined and transmitted.

It is understood that an ACK/NACK is an example of control informationwhich indicates whether data transmitted by a transmitting terminal issuccessfully received by a receiving terminal ACK/NACK is commonly usedfor HARQ. However, a random signal, for example, performing theabove-noted functions may be used as a replacement for ACK/NACK.

Subcarrier Mapping in Uplink

Various additional embodiments relate to subcarrier mapping in theuplink. In particular, such embodiments include arranging transmissiondata in a frequency resource allocated to the uplink in a wirelesscommunication system using a plurality of subcarriers and a transmitterimplementing the same.

FIG. 13 depicts localized allocation of a number of subcarriers. In thisfigure, localized allocation refers to user data that is transmitted viaa prescribed number of subcarriers, distributed adjacent to apredetermined band, among the entire band of a frequency resourceallocated for the uplink. User data is transmitted via subcarriers on apredetermined band only by inputting 0 to the remaining subcarriers.

According to the localized allocation, only a partial band of an uplinkfrequency resource is used. Yet, if transmission data is transmitted bya resource unit including a predetermined number of subcarriers, thetransmission data tends to be intensively arranged in a predeterminedarea within resource units consecutively allocated to a partial band ofthe frequency resource.

FIG. 13B depicts distributed allocation of a number of subcarriers. Inthis figure, distributed allocation refers to user data transmitted viasubcarriers equally distributed across entire bands of a frequencyresource allocated for the uplink. By inputting 0 to the remainingsubcarriers, the system can transmit the user data using only thedistributively allocated specific subcarriers.

The distributed allocation can distributively transmit the data acrossthe entire bands of the uplink frequency resource to raise frequencydiversity. So, it is advantageous that the distributed allocation isstrong against channel influence. However, as a pilot interval intransmitting a pilot using a short block gets wider than that intransmitting a pilot using a long block, channel estimation performancemay be degraded.

By way of overview, various embodiments include a method of arrangingsubcarriers for retransmission data distributively within an allocatedpartial band and a transmitter supporting the same. Channel influencemay be minimized using localized allocation.

One aspect includes arranging subcarriers for transmission datadistributively and a transmitter supporting the same. A predeterminednumber of the subcarriers are bound together to be distributivelyarranged according to localized allocation.

Another embodiment relates to a method of arranging subcarriers in theuplink, in which the subcarriers for data transmission are arranged in afrequency resource allocated for the uplink. One operation includesarranging the subcarriers for data transmission in a local band of thefrequency resource allocated for the uplink, such that the subcarriersare distributed with an equal space for a whole part of the local band.

According to one feature, the transmission data is a control signalrepeatedly coded with prescribed bits.

In another feature, the transmission data is transmitted via N (N=1, 2,3, . . . ) resource units, each having a prescribed number ofsubcarriers, and wherein the subcarriers are arranged in a manner ofarranging the N resource units in the local band of the frequencyresource allocated for the uplink and distributing the subcarriers withthe equal space across a whole band occupied by the N resource units.

In another aspect, a method of arranging subcarriers in the uplink, inwhich the subcarriers for data transmission are arranged in a frequencyresource allocated for the uplink, includes grouping the subcarriers forthe data transmission by at least two of the subcarriers across a wholeband of the frequency resource allocated for the uplink, wherein thegrouped subcarriers are distributed with an equal space.

Another feature relates to the transmission data transmitted via N (N=1,2, 3, . . . ) resource units, each having a prescribed number ofsubcarriers, and wherein the subcarriers are arranged in a manner ofdistributing the N resource units in the whole band of the frequencyresource allocated for the uplink with the equal space. The methodfurther includes grouping the subcarriers by at least two of thesubcarriers, and arranging the grouped subcarriers within each of the Nresource units.

In yet another aspect, an apparatus includes a subcarrier arrangingmodule arranging the subcarriers for the data transmission in a localband of the frequency resource allocated for the uplink, wherein thesubcarriers are distributed with an equal space for a whole part of thelocal band.

In one feature, the transmission data is transmitted via N (N=1, 2, 3, .. . ) resource units, each having a prescribed number of thesubcarriers, and wherein the subcarriers are arranged in a manner ofarranging the N resource units in the local band of the frequencyresource allocated for the uplink and distributing the subcarriers withthe equal space across a whole band occupied by the N resource units.

In another aspect, a transmitting apparatus for arranging subcarriers inthe uplink includes a subcarrier arranging module grouping thesubcarriers for the data transmission by at least two of the subcarriersacross a whole band of the frequency resource allocated for the uplink,wherein the grouped subcarriers are distributed with an equal space.

FIG. 14 is a block diagram depicting a method for uplink transmissionusing OFDM. At block 210, a high data rate data stream (or data symbol)is inputted in series and converted to a plurality of data streamshaving slow data rates via a serial to parallel converter. Each of theparallel-converted data streams is multiplied by a correspondingsubcarrier through a subcarrier mapper (block 220), and then transformedinto a time-domain signal by IDFT (block 230). Block 240 inserts acyclic prefix in the time-domain signal for preventing channelinterference. The signal is converted to a serial signal and thentransmitted to a receiving terminal (block 250).

It is understood that in a system performing modulation using aplurality of orthogonal subcarriers, OFDMA refers to the situation inwhich a multiple access method is accomplished by providing portions ofavailable subcarriers to different users. OFDMA provides different userswith frequency resources, such as subcarriers. Since the frequencyresources are independently provided to a plurality of users, they arenot overlapped with each other.

Since orthogonality is maintained between subcarriers, a high data ratecan be obtained. A possible problem that may arise relates to the peakto average power ratio (PAPR). To minimize or effectively eliminate thisproblem, spreading is carried out in the frequency domain using a DFTmatrix. This operation is typically performed before the generation ofan OFDM signal. The result of the spreading is modulated by OFDM toobtain a single carrier transmission. This situation may be referred toas DFT-S-OFDMA.

FIG. 15 is a flowchart depicting the generation of a transmission signalaccording to DFT-S-OFDMA. The technique is similar in many respects tothat which is shown in FIG. 1, such that blocks 310-340 generallycorrespond to blocks 110-140 of FIG. 1. A distinction is that cyclicprefix insertion (block 350) is shown occurring prior to theparallel/serial conversion of block 360.

In a multi-carrier system using OFDMA or DFT-S-OFDM, user equipmentdata, pilot, control information, and the like, are transmitted in theuplink. If the user equipment data is transmitted in the uplink,corresponding control information is transmitted in the downlink. Usingthe corresponding control information, a transmission band is allocatedor a data transport format is decided.

There are two general types of pilot signals. A CQ pilot is used tomeasure channel quality to perform UE scheduling and adaptive modulationand coding. A data pilot may also be used for channel estimation anddata demodulation in data transmission. The data pilot is the pilottransmitted on a corresponding domain. Control information may includedata-associated control information and non-data-associated controlinformation, as described above. The above-noted UE data, pilot, andcontrol information may be transmitted via a subframe having apredetermined structure. An example includes a FDD subframe for theuplink proposed by 3GPP LTE. A suitable subframe is depicted in FIG. 3A.

Referring back to FIG. 3A, a cyclic prefix (CP) is shown insertedbetween the respective blocks to avoid inter-block interference. In thisarrangement, the long block (LB) is usable for transmission of uplinkdata or control information, and the short block (SB) is usable fortransmission of uplink data or a pilot.

One method for multiplexing the subframe first includes multiplexing theUE data, pilot, and data-associated control information. Another methodfor multiplexing includes multiplexing the UE data, pilot, datademodulation associated control information, and data demodulationnon-associated control information. A third method for multiplexingincludes multiplexing the pilot and data demodulation non-associatedcontrol information.

Referring back to FIG. 7, data demodulation associated controlinformation and data demodulation non-associated control information fora specific user are shown multiplexed with UE data of a correspondinguser, and simultaneously, data demodulation non-associated controlinformation for other users is multiplexed together. This results ineach resource block including the same kind of uplink data.

Referring back to FIG. 8, data demodulation associated controlinformation for a specific user and UE data are multiplexed, but datademodulation non-associated control information for multiple usersincluding the specific user is transmitted via a separately providedpredetermined time-frequency domain (area indicated by slashes in FIG.8). Various kinds of data carried by the subframes, such as that whichis shown in FIGS. 7 and 8, may be multiplexed in the time domain tomaintain the advantage of the DFT-S-OFDM having low PAPR.

Since UE data for a specific user and data demodulation non-associatedcontrol information are multiplexed and transmitted for the samesubframe, it is common for the same kind of frequency allocation to beapplied to the UE data and the data demodulation non-associated controlinformation. In particular, if localized allocation is applied to the UEdata, it should be applied to the data demodulation non-associatedcontrol information as well.

As previously described, the ACK/NACK may be represented by a relativelyfew number of bits. The UE, for example, may repeatedly transmitACK/NACK for error rate enhancement. This may be accomplished using, forexample, the various techniques previously described with regard toFIGS. 3A and 3B.

Note that the repeated ACK/NACK can be transmitted via a resource unitthat is a bundle of a prescribed number of consecutive subcarriers. Theresource unit generally includes 25 long block frequency intervals,which does not appear to be a significant limitation. Alternatively, theresource unit may include long block frequency intervals of otherlengths (e.g., 15, 12, 10, and the like). The size of a normal resourceunit can be represented as:

RU=25*15KHz(LB)=375 KHz.

Hence, the localized allocation among the above-described frequencyallocation techniques is characterized in that N resource units areconsecutively allocated to a partial band. The distributed allocationamong the described frequency allocation methods is characterized inthat N resource units are discontinuously and equally allocated acrossentire bands.

In localized allocation, a frequency resource allocated to subcarriersfor ACK/NACK signal transmission is smaller than a frequency resourceoccupied by N resource units. As an example, FIG. 16 shows adistribution of subcarriers used for resource unit and ACK/NACKtransmission. In particular, N resource units are consecutivelyallocated to a partial band of an uplink frequency resource. Thesubcarriers used for repeated transmission of ACK/NACK signal amongsubcarriers included in the N resource units can be intensively arrangedon a specific band (central band in FIG. 16) of the frequency resourceoccupied by the N resource units. This case is referred to as purelocalized allocation.

As noted above, localized allocation is vulnerable to channel influencesince data is transmitted on an adjacent channel. Pure localizedallocation is more vulnerable to channel influence since the subcarriersof the transmission object included in the N resource units areintensively located on a specific band, as well as the N resource unitsbeing adjacent to each other.

To improve these vulnerabilities, enhanced localized allocation(distributed within allocated frequency resources) may be utilized. FIG.17 provides an example of a subcarrier arrangement using enhancedlocalized allocation. This technique applies distributed allocation tothe subcarriers of the transmission object included in the N resourceunits, while applying localized allocation to the N resource units. Inparticular, subcarriers actually used for transmission of ACK/NACKsignal are equally spaced and discontinuously arranged across the entirefrequency resource.

FIG. 18 shows a distribution of subcarriers used for ACK/NACK signaltransmission. The distributed allocation may be used to achievefrequency diversity. When a pilot is carried by a short block, a pilotinterval becomes wider than when a long block is used. Such anarrangement may not be preferable since channel estimation performancemay be degraded. An enhanced distributed allocation capable of enhancingchannel estimation performance may be achieved by grouping subcarriersfor ACK/NACK signal transmission into a plurality of groups, each ofwhich includes at least two subcarriers. These groups are then arrangedinstead of arranging the individual subcarriers.

FIGS. 19A and 19B depict a subcarrier arrangement using enhanceddistributed allocation, in which a pair of subcarriers is configured asa group. In FIG. 19A, since each subcarrier carries an ACK/NACK signalusing a long block, a frequency interval (e.g., 15 KHz) amounting to thelong block exists between a pair of the subcarriers configuring thecorresponding group.

In order to transmit an ACK/NACK signal to a receiving terminal, pilotinformation for matching synchronization between transmitting andreceiving terminals should be transmitted to the receiving terminal.Since it is unnecessary to transmit the pilot information for eachsubcarrier, the present embodiment implements one pilot that istransmitted for a pair of the grouped subcarriers. The pilot informationis carried by a short block. Since a frequency band (e.g., 30 KHz) of ashort block is generally twice as wide as that of a long block, itcoincides with the technique that one pilot is transmitted for each pairof the subcarriers for ACK/NACK signal transmission.

FIG. 19B shows frequency resource allocation of subcarriers for thepilot information transmission. Consider a grouping of subcarriers forACK/NACK signal transmission by a three-subcarrier unit, a frequencyband (15 KHz*3=45 KHz) occupied by one group is not equal to a frequencyband (30 KHz) occupied by the subcarriers for pilot transmission.Because of this, a gap of 30 KHz between the groups may be necessary(FIG. 20A). Since the subcarriers for pilot information transmission, asshown in FIG. 20B, should be arranged for each 60 KHz, channelestimation performance using a pilot is degraded rather than the case ofconfiguring a group with a pair of subcarriers.

As mentioned in the foregoing description, the enhanced localizedallocation or the enhanced distributed allocation is typically carriedout by a suitable subcarrier mapper (e.g., block 220 of FIG. 14) of theOFDM transmitting terminal or the subcarrier mapper of the OFDMAtransmitting terminal (e.g., block 330 of FIG. 15). Alternatively, theenhanced localized allocation or the enhanced distributed allocation canbe carried out by a subcarrier arranging module responsible for eachfrequency resource allocation.

A benefit of localized allocation permits efficient use of frequencyresources and arranges subcarriers for transmission data within thelocally allocated resource units. Hence, such an arrangement isprotected against channel influence in a manner that is greater thanexisting systems. Another benefit relates to the distributed allocationto avoid channel influence. This embodiment binds a predetermined numberof subcarriers for transmission, and arranges the subcarriersdistributively. Hence, compared to conventional systems, degradation ofchannel estimation is reduced.

Although embodiments of the present invention may be implemented usingthe exemplary series of operations described herein, additional or feweroperations may be performed. Moreover, it is to be understood that theorder of operations shown and described is merely exemplary and that nosingle order of operation is required.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses andprocesses. The description of the present invention is intended to beillustrative, and not to limit the scope of the claims. Manyalternatives, modifications, and variations will be apparent to thoseskilled in the art.

1. A method for transmitting uplink acknowledgments in response todownlink transmissions, the method comprising: receiving, in a UserEquipment (UE), a plurality of data blocks from a Node B, wherein eachof the data blocks include an associated cyclic redundancy check (CRC);determining received status for each of the data blocks by checking theCRC of each of the data blocks; generating a response sequence whichindicates the received status of all of the received plurality of datablocks; modulating the response sequence using QPSK modulation; andtransmitting, from the UE, the modulated response sequence to the NodeB, wherein the data blocks comprise a first transport block and a secondtransport block, wherein the received status is either an acknowledgment(ACK) which identifies a data block which has been received withouterror, or a negative acknowledgment (NACK) which identifies a data blockwhich has been received with an error.
 2. The method according to claim1, wherein the downlink transmissions comprise multiple input multipleoutput (MIMO) transmissions.
 3. The method according to claim 2, furthercomprising: receiving the data blocks in parallel.
 4. The methodaccording to claim 1, wherein the downlink transmissions comprise timedivision duplex (TDD) transmissions.
 5. The method according to claim 4,further comprising: sequentially receiving the data blocks.
 6. Themethod according to claim 4, further comprising: receiving the datablocks in parallel.
 7. A portable device for transmitting uplinkacknowledgments in response to downlink transmissions, the portabledevice comprising: a receiver configured to receive a plurality of datablocks from a Node B, wherein each of the data blocks include anassociated cyclic redundancy check (CRC); a processor configured todetermine received status for each of the data blocks by checking theCRC of each of the data blocks, to generate a response sequence whichindicates the received status of all of the received plurality of datablocks, to modulate the response sequence using QPSK modulation; and atransmitter for transmitting the modulated response sequence to the NodeB, wherein the data blocks comprise a first transport block and a secondtransport block, wherein the received status is either an acknowledgment(ACK) which identifies a data block which has been received withouterror, or a negative acknowledgment (NACK) which identifies a data blockwhich has been received with an error.
 8. The portable device accordingto claim 7, wherein the downlink transmissions comprise multiple inputmultiple output (MIMO) transmissions.
 9. The portable device accordingto claim 8, wherein the receiver is further configured to: receive thedata blocks in parallel.
 10. The portable device according to claim 7,wherein the downlink transmissions comprise time division duplex (TDD)transmissions.
 11. The portable device according to claim 10, whereinthe receiver is further configured to: sequentially receive the datablocks.
 12. The portable device according to claim 10, wherein thereceiver is further configured to: receive the data blocks in parallel.